As one of methods for chemically cleaning and disinfecting contact lenses, particularly soft contact lenses, there has hitherto been widely known a disinfection system using hydrogen peroxide. The hydrogen peroxide used therein is an effective disinfectant, and particularly attractive for disinfection of the contact lenses, because a decomposed product thereof is only water. However, such hydrogen peroxide is an active oxidant, so that the hydrogen peroxide should be completely removed from the contact lenses that were subjected to a disinfection treatment, before the contact lenses are worn again on the eye.
In a chemical disinfection method using such hydrogen peroxide, in order to obtain a desired disinfection effect, the hydrogen peroxide is generally required to have a concentration as high as about 3%, and a neutralization treatment for decomposing and detoxifying the hydrogen peroxide remaining on surfaces or in the insides of the contact lenses should be performed after disinfection. The reason for this is that the hydrogen peroxide inevitably remains on the surfaces or in the insides of the contact lenses after the disinfection, because the hydrogen peroxide is used at a relatively high concentration. The hydrogen peroxide remaining on or in the lenses may seriously damage the eye, even if the amount is small.
Thus, to the contact lenses subjected to the disinfection treatment by using the hydrogen peroxide, the neutralization treatment is conventionally applied. Specifically, the remaining hydrogen peroxide is removed by rinsing with a physiological saline, or completely decomposed and removed by using a metal catalyst such as platinum, a reducing agent such as sodium sulfite, sodium thiosulfate or pyruvic acid, an enzyme catalyst such as catalase or peroxidase, or the like. However, such a neutralization treatment generally makes a disinfection treatment operation of the contact lenses very cumbersome and complicated.
Accordingly, in order to easily perform the disinfection operation of the contact lenses using such hydrogen peroxide, JP-T-4-507052 discloses a vertical type contact lens case as an apparatus for sterilizing the contact lenses. In such a contact lens case, a hydrogen peroxide-containing sterilizing solution is contained, and the contact lenses to be treated and a catalyst agent are disposed therein so as be in contact with the sterilizing solution. As a result, the contact lenses are disinfected or sterilized, while a neutralization treatment is performed in which the hydrogen peroxide in the sterilizing solution is decomposed with the catalyst agent. The neutralization rate of the hydrogen peroxide in such a sterilizing solution depends on the amount of catalyst (metal) in the catalyst agent. In order to completely remove the hydrogen peroxide effectively from the contact lenses, the neutralization efficiency needs to be increased by improving the neutralization rate without influencing a disinfecting effect on the lenses. For this purpose, the amount of the catalyst metal needs to be increased. Further, the catalyst agent (catalyst metal) used herein needs to be replaced with a new one at a predetermined time intervals in order to assure the safety, for example. Accordingly, in the disinfection system using the hydrogen peroxide, it is a major object to reduce the amount of the catalyst metal in terms of cost reduction.
Further, JP-A-63-274602 discloses a stabilized hydrogen peroxide solution including a hydrogen peroxide solution, and a peroxide stabilizer composed of a predetermined sulfonic acid compound and a secondary peroxide stabilizer such as glycerin or polyvinyl alcohol, which are added to the hydrogen peroxide solution. It also discloses that the sterilization by heat can be performed in combination by the use of this stabilized hydrogen peroxide solution as a disinfecting solution of contact lenses, resulting in the reduction of time for immersing lens materials in the disinfecting solution. However, it discloses that the hydrogen peroxide must be removed after the disinfection treatment, and in order to remove it, the contact lenses are rinsed or a known hydrogen peroxide-decomposing material is allowed to be in contact with the solution, after the disinfection treatment.
Furthermore, WO2002/26922 proposes a technique of inhibiting foaming at the time of a disinfection operation of contact lenses by allowing a surfactant composed of a block copolymer having a hydrophobic block and a hydrophilic block to be contained in a contact lens disinfecting solution containing an effective disinfecting amount of hydrogen peroxide. In addition, JP-A-3-278837 discloses a method of disinfecting contact lenses by using a hydrogen peroxide-decomposing catalyst in which manganese oxide, cobalt oxide or copper oxide is carried on an inorganic carrier. However, these Patent Documents do not disclose in any way that the disinfection of the contact lenses is effectively performed by increasing the neutralization rate of the hydrogen peroxide in the disinfecting solution to improve its neutralization efficiency by using a specific composition of the disinfecting solution, in other words, by adding specific components to the disinfecting solution.
As described above, various disinfection systems of contact lenses using hydrogen peroxide solutions have conventionally been proposed. However, none of them has proposed or reported any composition of solution for increasing the neutralization rate of hydrogen peroxide to improve its neutralization efficiency, while securing the effective disinfection effect by a hydrogen peroxide-containing solution (disinfecting solution).